Microstructural Control of Fatigue Behaviour in a Novel  Titanium Alloy

• Main Authors: Martin Bache, Helen Davies, William Davey, Matthew Thomas, Iain Berment-Parr
• Format: Article
• Language: English
• Published: MDPI AG 2019-11-01
• Series: Metals
• Subjects: ti-407; dwell sensitive fatigue; quasi-cleavage facets; micro-texture; macro-zones
• Online Access: https://www.mdpi.com/2075-4701/9/11/1200

The novel titanium alloy TIMETAL^® 407 (Ti-407) has been developed as an alternative to Ti-6Al-4V (Ti-6-4), for applications that demand relatively high ductility and energy absorption. Demonstrating a combination of lower strength and greater ductility, the alloy introduces a variety of cost reduction opportunities, including improved machinability. Thermo-mechanical processing and its effects on microstructure and subsequent mechanical performance are characterised, including a detailed assessment of the fatigue and crack propagation properties. Demonstrating relatively strong behaviour under high-cycle fatigue loading, Ti-407 is nevertheless susceptible to time-dependent fatigue effects. Its sensitivity to dwell loading is quantified, and the associated deformation and fracture mechanisms responsible for controlling fatigue life are explored. The intimate relationship between thermo-mechanical processing, micro-texture and fatigue crack initiation through the generation of quasi-cleavage facets is highlighted. Consistent fatigue crack growth kinetics are demonstrated, independent of local microstructure.